The invention addresses lubrication problems of two cycle crankcase compression internal combustion engines, including but not limited to marine propulsion system applications. The invention provides a valve which automatically mixes fuel and oil, and eliminates the need to premix same.
The valve has a fuel inlet, an oil inlet, and an oil-fuel outlet, and operated by a pressure differential between the fuel inlet and the oil-fuel outlet. A feature of the invention is that only a very small pressure differential is needed to operate the valve because there is no spring gradient against a diaphragm to be overcome. For example, the valve may be connected upstream of the fuel pump such that fuel pump vacuum on the oil-fuel outlet operates the valve. This implementation is advantageous because it can be adapted to any engine without internal or external modifications to the engine. In contrast, a gear driven pump type of premixing system is costly because of the extensive engine modifications needed.
The mixing valve of the invention is further characterized by its versatility. The mixing valve may be connected downstream of the fuel pump and use the fuel pressure to operate the mixing valve. In other applications where a pressurized fuel tank is utilized, such pressure may be used to operate the valve. In other implementations, crankcase pressure and/or vacuum may be used to operate the valve, or a separate dedicated small pump may be used.
The invention further provides a fail-safe mixing valve. In the event of valve failure, the supply of fuel is halted.